HYDROLYSED SALMON MEAL AS A REPLACEMENT FOR SALMON MEAL IN PRACTICAL DIETS FOR PACIFIC WHITE SHRIMP Litopenaeus vannamei
Given that the nutrient profile of salmon meal (SM) and hydrolyzed salmon meal (HSM) are similar this provides a good model to evaluate the use of silage products in feeds. A series of growth, feed stability and consumption trials were conducted to evaluate the efficacy of salmon by-product meal (SM and HSM) in practical diets for Pacific white shrimp, Litopenaeus vannamei. This included a meal produced under traditional processing (SM) and one produced by a hydrolysis process (HSM). The basal diet contained12% SM, which was incrementally replaced (0. 25, 50, 75, 100%) on an isonitrogenous basis to produce five test diets used in two growth trials. A sixth diet was included which evaluated gelatin supplementation (Trial 1) or pH neutralization (Trial 2). In trials 1 and 2, juvenile shrimp (initial weight 0.17 g and 0.24g) were hand-sorted to uniform size and randomly stocked into 75-L aquaria or 800 L circular tanks which are a component of a 2.5 m3 or 21 m3 recirculation system at 10 shrimp per aquarium or 30 shrimp per tank, respectively. In trial 1, each diet was produced using two processing conditions (laboratory extruded and formed with meat grinder) and offered to shrimp over 42-day in a clear water RAS system. The results showed that 5.85% HSM can be used to replace salmon meal without an effect on the growth performance of the shrimp. Diets with the highest level of HSM had reduced stability and a lower pH as compared to the basal diet. Leaching of aromatic amino acids (AA) was evaluated across the diets. There is clear increase in AA leaching as the level of HSM increases in the diet. The addition of gelatin reduced leaching but there was limited effect of processing on leaching. Trial 2 was conducted over 56-day in an outdoor green water system. Results indicated that up to 6.08% HSM can be used to replace 50% salmon meal without effect the growth performance of the shrimp. There was no effect of pH adjustment on shrimp performance. Based on the observed results, HSM is a suitable protein source for shrimp feeds but it is recommended to limit the inclusion of HSM to 6% of the diet.
